Sorted By Test Name - Mayo Medical Laboratories

ACRN
82413
Acylcarnitines, Quantitative, Plasma
Clinical Information: Acylcarnitine analysis enables the diagnosis of many disorders of fatty acid
beta oxidation and several organic acidurias, as relevant enzyme deficiencies cause the accumulation of
specific acyl-CoAs. Fatty acid oxidation (FAO) plays a major role in energy production during periods of
fasting. When the body's supply of glucose is depleted, fatty acids are mobilized from adipose tissue,
taken up by the liver and muscles, and step-wise oxidized to acetyl-CoA. In the liver, acetyl-CoA is the
building block for the synthesis of ketone bodies, which enter the blood stream and provide an alternative
substrate for production of energy in other tissues when the supply of glucose is insufficient to maintain a
normal level of energy. The acyl groups are conjugated with carnitine to form acylcarnitines, which are
measured by tandem mass spectrometry (MS/MS). Diagnostic results are usually characterized by a
pattern of significantly elevated acylcarnitine species compared to normal and disease controls. In general,
more than 20 inborn errors of metabolism can be identified using this method including FAO disorders
and organic acidurias. The major clinical manifestations associated with individual FAO disorders include
hypoketotic hypoglycemia, variable degrees of liver disease and/or failure, skeletal myopathy,
dilated/hypertrophic cardiomyopathy, and sudden or unexpected death. Organic acidurias also present as
acute life-threatening events early in life with metabolic acidosis, increased anion gap, and neurologic
distress. Patients with any of these disorders are at risk of developing fatal metabolic decompensations
following the acquisition of even common viral infections. Once diagnosed, these disorders can be treated
by avoidance of fasting, special diets, and cofactor/vitamin supplementation. In these groups of disorders,
characteristic metabolites accumulate in blood and bile as carnitine derivatives. Analysis of acylcarnitines
in blood and bile spots represents the first level of evaluation of a complete postmortem investigation of a
sudden or unexpected death of an individual. Additional confirmatory testing is recommended. The
diagnosis of an underlying FAO disorder or organic aciduria allows genetic counseling of the family,
including the possible option of future prenatal diagnosis, and testing of at-risk family members of any
age. Disorders Detectable by Acylcarnitine Analysis* Fatty Acid Beta-Oxidation Disorders: -Short-chain
acyl-CoA dehydrogenase (SCAD) deficiency -Medium/Short-chain 3-hydroxyacyl-CoA dehydrogenase
(M/SCHAD) deficiency -Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency -Long-chain
3-hydroxyacyl-CoA dehydrogenase (LCHAD) deficiency & trifunctional protein deficiency -Very
long-chain acyl-CoA dehydrogenase (VLCAD) deficiency -Carnitine palmitoyl transferase type II
(CPT-II) deficiency -Carnitine-acylcarnitine translocase (CACT) deficiency -Electron transfer
flavoprotein (ETF) deficiency, ETF-dehydrogenase deficiency (multiple acyl-CoA dehydrogenase
deficiency [MADD]; glutaric acidemia type II) Organic Acid Disorders: -Glutaryl-CoA dehydrogenase
deficiency (glutaric acidemia type I) -Propionic Acidemia -Methylmalonic Acidemia -Isovaleric
Acidemia -3-hydroxy-3-methylglutaryl-CoA carboxylase deficiency -3-Methylcrotonyl carboxylase
deficiency -Biotinidase deficiency -Multiple carboxylase deficiency -Isobutyryl-CoA dehydrogenase
deficiency -2-Methylbutyryl-CoA dehydrogenase deficiency -Beta-ketothiolase deficiency -Malonic
aciduria -Ethylmalonic encephalopathy *Further confirmatory testing is required for most of these
conditions because an acylcarnitine profile can be suggestive of more than 1 condition.
Useful For: Diagnosis of fatty acid beta-oxidation disorders and several organic acidurias Evaluating
treatment during follow-up of patients with fatty acid beta-oxidation disorders and several organic
acidurias
Interpretation: An interpretive report is provided. The individual quantitative results support the
interpretation of the acylcarnitine profile but are not diagnostic by themselves. The interpretation is based
on pattern recognition. Abnormal results are not sufficient to conclusively establish a diagnosis of a
particular disease. To verify a preliminary diagnosis based on an acylcarnitine analysis, independent
biochemical (eg, in vitro enzyme assay) or molecular genetic analyses are required. For information on
the follow-up of specific acylcarnitine elevations, see Special Instructions for the following algorithms:
-Newborn Screening Follow-up for Elevations of C8, C6, and C10 Acylcarnitines (also applies to any
plasma C8, C6, and C10 acylcarnitine elevations) -Newborn Screening Follow-up for Isolated C4
Acylcarnitine Elevations (also applies to any plasma C4 acylcarnitine elevation) -Newborn Screening
Follow-up for Isolated C5 Acylcarnitine Elevations (also applies to any plasma C5 acylcarnitine
elevation)
Reference Values:
Current as of January 4, 2013 7:15 pm CST 800-533-1710 or 507-266-5700 or MayoMedicalLaboratories.com Page 50